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% iron - sulphuric acid pickling - steel wire rod?

% iron - sulphuric acid pickling - steel wire rod?

% iron - sulphuric acid pickling - steel wire rod?

(OP)
I would like to know if the following testing method for iron % in sulfuric acid - steel wire rod pickling is correct and if any other exist?

first - % acid  

            -    Add 5 mls of acid solution in a 250  mls becker.
            -    Add 100 mls of water.
                -       Add 4 drops of methyl orange
                -       use carbonate sodium until color change to yellow
                      keep same solution
second  - %iron
            -    add 5 mls of sulfuric acid
            -    use potassium permaganate until color change (light pink).

          NOTE:    number of mls (1.on) used of permanganate potassium x 1.44= % iron


thanks

RE: % iron - sulphuric acid pickling - steel wire rod?

You've omitted some necessary details for the acid analysis; the iron analysis is  partially correct but may still be useful.

I have added the conversion for sulfuric acid to procedures for hydrochloric acid pickling solution; H+ is H+.
It's probably more common to use sodium hydroxide solution than carbonate solution for acid titrations, but either works as long as you know  the normality.  The procedure I use for HCl-containing solutions is this:

Hydrochloric (or sulfuric) acid:
  1.  Pipet a 2 ml sample into a 250 ml beaker and add 100 ml DI water.
  2.  Add 5 mLs of 20%(w/v) KF (avoids Fe+3 precipitation).
  3.  Titrate to pH = 3.8 using 1 N NaOH.

    [HCl (36 wt%)], vol.% = 4.356 x mls of 1 N NaOH.
   or   [H2SO4 (98 wt%)], vol.% = 1.33 x mls of 1 N NaOH.

Using a 5-mL sample & methyl orange indicator with 1 N  NaOH titrant, the HCl concentration is given as
    [HCl (36 wt%)], vol. % =  1.74 x mls of 1 N  NaOH
  or    [HCl (32 wt%)], vol. % =  1.96 x mls of 1 N  NaOH
  or   [H2SO4 (98 wt%)], vol.% = 0.532 x mls of 1 N NaOH.
A 1 N carbonate titrating solution should give the same results.

IRON analysis.  Your oxidation titration only gives [Fe+2], not [Fe+3] ( the predominant Fe species present in yellow solutions).  
Try adding hydrogen peroxide to a sample to see all Fe as Fe+3, or sodium thiosulfate for entirely Fe+2.  Also, I suggest not using wt% unless also measuring the specific gravity (SG).

  [Fe+2], g/L = 11.1 x mLs 0.1 N KMnO4 or 1.11 x mLs 1.0 N KMnO4

For total [Fe], you can first titrate all Fe+3 to Fe[sup+2[/sup] by reduction with 0.1 N  sodium thiosulfate (no excess, can do by ORP or color), then titrate all the Fe+2 by oxidation with 0.1 N KMnO4.  Or, calculate the [Fe+3] from the reduction titration and add it to the [Fe+2] from your original oxidation titration.

Maybe only necessary to do the [Fe+2] analysis as you already have data on the pickling behavior.  Also, some people determine [Fe] by careful SG measurement after adjusting both [acid] and temperature to standard values, but this is a bit crude.

RE: % iron - sulphuric acid pickling - steel wire rod?

Adding a little to kenvlach's I would use a polyethylene or teflon beaker for the first step. The HF is hard on glass.

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